Ion exchange

ABSTRACT

An ion exchange material comprising a superabsorbent polyurethane foam having an ion exchange medium contained therein. The ion exchange may be used in a process for the extraction of metal anions and cations from solutions and/or slurries including the steps of: (a) contacting a metal ion-containing solution with an ion exchange material comprising a superabsorbent polyurethane foam having an ion exchange medium contained therein; (b) separating the ion exchange material from the solution and/or slurry; and (c) recovering the sorbed metal ions from the ion exchange medium.

The present invention relates to ion exchange, in particular to ionexchange materials embedded in a polyurethane matrix. The presentinvention also relates to a process for the recovery of metal cationsand anions from solutions and slurries.

Ion exchange resins are generally manufactured in bead or particulateform from polymers such as polystryrene-divinyl benzene, acrylic, orphenol-formaldehyde condensates. It has been proposed that ion exchangefibres can be produced from either polyacrylonitrile onto which activeligands can be attached, or polypropylene fibres on to whichpolystyrenedivinyl benzene can be grafted. Polyurethane foams have beenproposed in PCT/AU93/00312 and PCT/AU94/00793 which are incorporatedherein in their totality by reference.

Ligands can be attached to the surface of the particular ion exchangeresins or fibres by conducting one or more suitable chemical reactions.

Commercially manufactured resins have several disadvantages, includingsmall particle size to provide a large surface-to-volume ratio, oftenlower selectivity for one metal ion species over other metal ion speciesprevalent in leach liquors and pK_(a) values which prevent the resinloading anions at pH values above about 10. Additional ligand capacityis provided by making the resin beads macroporous. This may be achievedby incorporating one or more porogens into the resin system during thepolymerisation step. Such macroporosity, can lead to increasedshattering of the beads in industrial processes.

The bulk density of the beads are not readily modified. Thus, the ionexchange beads being offered for application in for example, the goldindustry have a tendency to float on the surface of the pulp during thecyanidation step. It is reported that this has led to loss of gold dueto pilferage of the loaded beads.

In an effort to overcome this disadvantage, U.S. Pat. No. 4,284,511which is incorporated here by reference, describes the addition ofmagnetic material, particularly finely divided particles of anon-corrosive, iron-chrome alloy to raise the bulk density of thepolymer. This addition is proposed to be used with activated carbon, andpolyurethane and similar materials when used in ion exchange columns,and in particular, in fluidised bed towers to enable higher fluid flowrates to be achieved.

Other disadvantages of currently available ion exchange resins for metalion recovery include:

-   -   (a) purchase cost is high,    -   (b) the present need for fine sized beads (in order to achieve a        significant concentration of ligands) renders it difficult to        recover them from pulps by screening,    -   (c) stripping kinetics are slower and a more complex stripping        regime is often required to effectively recover the metal ion        for electrowinning.

We have now found that by embedding an ion exchange material in asuperabsorbent polyurethane foam we are able to achieve superior ionexchange performance. The present invention accordingly provides an ionexchange material comprising a superabsorbent polyurethane foam havingan ion exchange medium contained therein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph showing the differences in gold loading between ionexchange resins containing a superabsorbent polyurethane and ionexchange resins without a superabsorbent polyurethane.

FIG. 2 is a graph showing the differences in copper loading between ionexchange resins containing a superabsorbent polyurethane and ionexchange resins without a superabsorbent polyurethane.

The present invention also provides a process for the extraction ofmetal anions and cations from solutions and/or slurries including thesteps of:

-   -   (a) contacting a metal ion-containing solution with an ion        exchange material comprising a superabsorbent polyurethane foam        having an ion exchange medium contained therein;    -   (b) separating the ion exchange material from the solution        and/or slurry; and    -   (c) recovering the sorbed metal ions from the ion exchange        medium.

These superabsorbent, hydrophilic polyurethane polymers are chemicalentities which are well known to those skilled in the art. Methods forthe preparation or application of these polymers are typically describedin U.S. Pat. Nos. 3,793,241; 3,854,535; 3,861,993; 3,890,254; 3,900,030;3,903,232, 3,904,557; 4,110,508; 4,127,516; 4,137,200; 4,158,087;4,160,076; 4,181,770; 4,266,043; 4,292,412; 4,314,034; 4,365,025;4,337,645; 4,384,050; 4,384,051; 4,717,738; 4,725,628; 4,731,391;4,740,528; 4,789,720; 4,798,876; 4,828,542; 5,065,752; 5,296,518;5,591,779 and 5,624,971, which are incorporated herein by reference.

The procedure for the manufacture of the prepolymers described in theabove patents is either given within the description, or can be producedaccording to typical procedures as described in various publicationsrelating to polyurethane chemistry, or as disclosed in U.S. Pat. Nos.2,726,219; 2,948,691; 2,993,013; 3,805,532 and 4,137,200.

In U.S. Pat. No. 4,725,629 a superabsorbent polyurethane foam isdescribed which is based upon an interconnecting polymer network of across-linked polyurethane and a cross-linked addition polymer containera plurality of chain segments made up of functional groups containingrepeating units which may be the same of different. These superabsorbentpolymers are recommended for the manufacture of absorbent articles,especially disposable absorbent articles, such as nappies, sanitarynapkins, bedpads, incontinent pads, and the like.

Superabsorbent polyurethane foams preferably derived from anisocyanate-terminated poly(oxyalkylene) polyol having an isocyanatefunctionality greater than two and containing an addition polymer suchas acrylamides, acrylate and methacrylate salts, etc. are disclosed inU.S. Pat. No. 4,731,391.

British Patent 1,209,058 discloses a hydrophilic polyurethane foam inwhich a polyether polyol containing a block of ethylene oxide cappedwith propylene oxide to obtain hydrolytic stability is reacted with apolyisocyanate. Only small quantities of water are used. The foamsproduced by this method have very poor water absorbing properties.

A superabsorbent polyurethane foam into which microcapsules of activeingredients are formed is described in U.S. Pat. No. 4,828,542. Thehydrophilic polyurethane prepolymer is foamed by mixing with water inthe range of at least approximately 0.2/1 or greater and preferably 1/1or greater.

U.S. Pat. No. 5,065,752 describes a superabsorbent, hydrophilic foamcomposition for wound dressings. The polyurethane foam is produced bythe in-situ reaction product of an isocyanate-capped polyetherprepolymer, a polymeric hydrophilic agent capable of absorbing water(such as starch grafted copolymers of acrylate salts, or acrylamidesalts), an adjuvant comprising a water-soluble alcohol, a wetting agent,and water.

U.S. Pat. No. 5,591,779 discloses a process for preparing asuperabsorbent polyurethane foam by reacting a suitable polyurethaneprepolymer with water in the presence of a superabsorbent polymer. Thepolyurethane prepolymer contains an oxyethylene content of at least 50%by weight. The amount of water required being 15 to 500 parts by weightof the weight of the prepolymer. At the start of the reaction, thetemperature of the water being 10° C. to 50° C. higher than thetemperature of the prepolymer.

The ion exchange medium may be any convenient ion exchange mediumsuitable for sorbbing the desired metal ions from the solution and/orslurry. The ion exchange medium may be in the form of a bead, resin,fibre, foam, or liquid.

Ion exchange mechanisms generally involve the exchange of ions insolution with the counter ions associated with the ligands present inthe extractant. The extractant may be either an insoluble solidinorganic or organic material, or a water-insoluble organic molecule.Thus, the desired extractant therefore contains anionic, cationic, orchelating ligands capable of recovering the desired metal ion fromeither solutions or from slurries.

Normally a metal ion exists in an aqueous solution as a hydrated ionwith little or no tendency to transfer to an organic phase. To enable anion to transfer into an organic phase it is generally required that itscharge must be neutralised and some, or all of its water of hydrationhas to be replaced by some other molecule or ion. For example, asreported by Irving and Damodaran the aurocyanide anion is generallyweakly hydrated compared to other cyano-metallic complexes. Thus, itsaffinity for organic matrices relative to other more strongly hydratedanions, will be greater. A study on ionic mobilities in the Nernst layerhas shown that the aurocyanide complex is significantly smaller and lesshydrated than other cyano complexes. Examination of the hydration andion pairing of the Au (CN)_(n) ⁻ complex in aqueous solution doeshowever require further investigation. Therefore, for a metal ion to beremoved from the aqueous phase, these conditions can be met by:

-   -   (a) complexing the ion with an ion of opposite charge to form a        neutral species, which at the same time replaces some or all of        the water of hydration around the metal ion,    -   (b) by formation of ion-association complexes which also provide        for the formation of a neutral species with the extractant,    -   (c) by replacing the water of hydration with molecules of the        extractant.

An ion exchange medium, thus, may be a polymeric material inparticulate, bead, fibre or foam form which carries a fixed positive ora fixed negative electrical charge. This electrical charge is balancedby ions of opposite sign, called counter ions. In solution, thesecounter ions are free to move within the resin matrix and therefore canbe replaced, or exchanged, by other ions of the same sign. Thus systemsemploying chelating and acidic extractants are cation-exchangereactions, and those employing anion exchange systems are anion-exchangereactions.

Extractants containing C—O bonds are electron donating compounds, butalcohols being amphoteric, exhibit both donor and acceptor propertiesand resemble water in many ways. Thus, the formulation of superabsorbentpolymers based upon poly(oxyethylene) glycol, and if required sulphonicgroups in the polymer structure, will enhance metal ion transport.Alcohols such as pentanol, n-hexanol, 2-ethylhexanol, isodecanol,dodecanol, tridecanol, hexadecanol, octadecanol; phenols such asheptylphenol, octylphenol, nonylphenol and dodecylphenol may be includedinto these superhydrophilic foams to improve salvation and also metalion transport. The need for hydrophilicity in the polymer to enhance themetal ion loading is demonstrated by Chiariza, R., et al., Diphonix®resin: A review of its properties and applications, Sep. Sci. andTechnol—(1997), 32 (1–4), 1–35.

The preferred aromatic isocyanates are 2,4- and 2,6-toluenediisocyanates and methylene-bridged polyphenyl polyisocyanate mixtureswhich have a functionality of from about two to about four. These latterisocyanate compounds are generally produced by the phosgenation ofcorresponding methylene-bridged polyphenyl amines, which areconventionally produced by the reaction of formaldehyde and primaryaromatic amines, such as aniline, in the presence of hydrochloric acidand/or other acidic catalysts. Known processes for preparing polyaminesand corresponding methylene-bridged polyphenyl polyisocyanates therefromare described for example in U.S. Pat. Nos. 2,683,730, 2,950,263,3,012,008, 3,344,162 and 3,362,979.

Most preferred methylene-bridged polyphenyl polyisocyanate mixtures usedherein contain about 20 to about 100 weight percent methylenediisocyanate isomers, with the remainder being polymethylene polyphenylisocyanates having higher functionalities and higher molecular weights.Typical of these are polyphenyl polyisocyanate mixtures containing about20 to 100 weight percent methylene diphenyldiisocyanate isomers, ofwhich 20 to about 95 weight percent thereof is the 4,4′-isomer with theremainder being polymethylene polyphenyl polyisocyanates of higherweight and functionality of from about 2.1 about 3.5. These isocyanatemixtures can be prepared by the process described in U.S. Pat. No.3,332,979.

A commercially available MDI compound with especially desirableproperties is Isonate 143L which is produced by reacting MDI to form thecarbodiimide and this material in turn reacts to form a tri-functionalcycloadduct. The mixture of MDI, the carbodiimide and the cycloadductare in equilibrium. The mixture contains a major amount of purediphenylmethane diisocyanate and minor amounts of carbodiimides andtrifunctional cycloadducts of diphenylmethane diisocyanate. Asdescribed, the term derivatives of diphenylmethane diisocyanate meanproducts that have been made from MDI as a starting material. Itincludes adducts dimmers, and trimers.

Other compounds which are useful are the isocyanate equivalents whichproduce the urethane linkages such as the nitrile carbonate, includingthe adiponitrile carbonate.

Also, both ethers and ketones allow a high degree of metal hydration inthe solvent phase. For example, in the extraction of ferric chlorideinto ether, five molecules of water are associated with the extractedmetal complex in the solvent phase and solvation numbers as high as 12have been reported. Thus, superhydrophilicity enables these watermolecules to be rapidly transported through the polymer to the reactivesites.

The preferred components include a diol having greater than about 80% byweight of poly(oxyethylene) groups (such as PEG 1000) to provide thewater-absorbing property, trimethylolpropane as the crosslinking agent,suspending or thickening agents and the isocyanate used to cap orterminate the polyol is as described above.

The poly(oxyethylene) polyol may have a molecular weight of about 200 toabout 20,000 and preferably between about 600 to about 6,000 and mostpreferably about 1000 to about 1400, with a hydroxyl functionality ofabout 2 or greater, but preferably from about 2 to 6 and mostpreferably, 2.

The chain extenders which may be added to provide crosslinking strengthto the foam are relatively short, low molecular weight monomeric polyolshaving three or four hydroxyl equivalents per mole. Such materialsinclude glycerol, trimethylolpropane, trimethylolethane,triethanolamine, pentaerithritol, or mixtures thereof.

Suspending or thickening agents include acrylic acid-based polymers suchas Carbopol 934 and Carbopol 940. A neutralising agent such as sodium orammonium hydroxide can be added.

The capping or termination reaction between the isocyanate and thepolyol may be carried out in an inert moisture-free atmosphere such asunder a nitrogen blanket, at atmospheric pressure at a temperature inthe range of about 0° C. to about 120° C. for a period of time of up toabout 24 hours depending upon the temperature and the degree ofagitation and cooling or heating applied to the reactor.

Superabsorbant microcellular resins and foams differ from polyurethanefoams in that they are normally produced by the reaction of a suitablyformulatend isocyanate terminated polymer with a very significant excessof water. The polyol portion of the polymer is generally based uponpoly(oxyethylene) glycol, and the isocyanate component is generally TDI,MDI or MDI-based isocyanate or mistures of both isocyanantes.

Another very desirable property of the instant foams is the eliminationof silicone surfactants from the formulation. It has been observed thatthese nonionic silicone-based raw materials are specifically formulatedso that they migrate to the surface of the rising foam to control thesurface tension, promote nucleation and stabilise the rising foam byreducing stress concentrating in thinning cell-walls and counteract anydefoaming effects caused by the presence of added, or generated/solidmatter. Thus, these polymers remain at the surface of the curedpolyurethane foam and interfere with subsequent interpenetration of asecond polymer or surface reactions conducted on the polyurethane foamcell walls.

The use of water soluble or water dispersable-surface active agents inurethane-urea foams is taught in U.S. Pat. Nos. 3,890,254 and 4,160,076to be critical to the attainment of many useful properties. Whereas, inU.S. Pat. No. 5,296,518 it was recognised that the choice of certainisocyanate-capped high molecular weight molecules can be used in placeof these surfactants. Being water soluble, and not taking part in thechemical reaction, they can be leached out of the foam. Thus, thepresence of these surface active agents does not interfere withsubsequent surface reaction such as interpenetration of a second polymersystem.

The level of surfactant may be varied from 0% to about 5% based upon thetotal water content of the formulation. If low levels of surfactant areused higher density foams will generally result. Such polymers will haveadvantage in applications in which the final product is required tooffer improved abrasion resistance. In the present invention thePluronic series of surfactants manufactured by BASF are preferred, withPluronic L62 being particularly preferred in this aspect.

Thermal reticulation may be advantageously conducted whereby the windowsor membranes are removed from individual cells or bubbles which make upthe foam structure. Reticulation results in a foam preferably having atleast 95% of open cells and most preferably 99% open cells. Thermalreticulation of polyurethane foam is a known procedure to those skilledin the art and as disclosed for example in U.S. Pat. Nos. 3,171,820 and3,875,025 and 3,175,030. Reticulation is achieved by providing acombustible mixture of an oxidizer material and an oxidisable materialwithin whereupon the cell windows or membranes are destroyed. It is alsopossible to swell the polyurethane foams in an organic solvent toincrease the cell size.

Thus, as disclosed in U.S. Pat. No. 4,985,467, the skeletal structure iscompletely open, and with such a structure, it will more rapidly absorblarge amounts of liquid than an a non-reticulated cellular foam.

Poly(ethylene oxide) derivatives are good solvents for metal ionsbecause of the Lewis-base nature of the lone pairs on the oxygen atom.Macrocycles based on the ethylene oxide unit, the crown ethers, areamongst the strongest known complexing agents for cations. The reasonfor this is twofold, namely, the rings formed by ethylene oxide unitstend to place oxygen atoms in favourable positions for the formation ofcoordination bonds with metal cations; and secondly, the excellentsolvating properties of poly(ethylene oxide).

To produce the desired superabsorbent ion exchange resins, severaldifferent methods may be adopted. In one preferred method, commerciallyproduced solid ion exchange polymers may either be comminuted to reducetheir particle size, or they may be used directly in the resin formingstep, details of which appear below.

Alternatively, an another preferred method, organic liquid ion exchangematerials may be imbibed into a solid sorbent in a suitable form such asparticulates, sheets, fibres, foams. Such solid sorbents includestyrene-divinyl benzene, acrylic, phenolformaldehyde, polyvinylchloride, carbon, zeolites, vermiculite, etc and then incorporated intothe superabsorbent resin.

Whilst the extractants may be imbibed into pulverised materials, it isalso acceptable that highly porous materials, such as activated carbon,granules be used. The extractant can be imbibed into these materials,preferably under reduced pressure to remove entrapped air form withinthe porous material. A dilute coating of the prepolymer, such as isdescribed in Example 7, may then be applied to the outer surface of thebeads.

A further method is to melt a suitable wax such as petroleum wax,beeswax, a mixture of waxes etc., in hot water containing a suitablesurfactant such as Pluronic L62 manufactured by BASF and add the liquidion exchange or extractant mixture whilst stirring to form an emulsion.Continue stirring during cooling to room temperature to from an aqueousemulsion dispersion of the organic mixture in water. This aqueousemulsion is then used as part of the aqueous phase for production of thesuperhydrophilic polymer.

TBP addition to an uncharacterised polyurethane foam for the recoveryand separation of nickel and palladium is described by Braun and Farag,Talanta (1972), 19, 828–830. This foam would not have providedsufficient hydrophilicity as enunciated in the present disclosure.

A number of phosphates, including di(2-ethylhexyl) phosphate, andparticularly tri-n-butyl phosphate (TBP) have been extensively employedin solvent extraction systems for metal ions. TBP has been included in anumber of patents relating to gold recovery from chloride and cyanidesolutions. It is used in industrial process to remove arsenic fromcopper solutions. It is proposed as a suitable extractant for zinc fromacid solution.

As a general rule, the extractive power of phosphorous containingextractants increases with an increase in the number ofcarbon-phosphorous bonds over the series,phosphate-phosphonate-phosphine oxide. The solubility of neutralorganophosphorus compounds in water decreases in the order phosphineoxides>phosphinates>phosphonates>phosphates. This is as a result of theincreasingly polar nature of the phosphonyl group. It should be notedthat in acid solutions these extractants have low solubility, but as thepH increases, so solubility increases. It is known that the phosphoryloxygen forms hydrogen bonds with water, and the bond energy isapproximately 5 kcal/mole. The more basic oxygen in a phosphonate givesa hydrogen bond energy of about 7–8 kcal/mole.

Dialkyl phosphorodithioioic acids, phosphonates, dialkylthiophosphate,sulphur-containing methyl phosphonates and ketophosphonates and thetrialkyl thiophosphates have been shown to be highly selective for gold,silver and mercury. Triiso-octyl thiophosphate and tri-n-butylthiophosphate are similar to their trialkyl phosphate counterpartsexcept that the P═O has been replaced by a P═S group. The semipolarsulphur atom is the sole structural difference between the two types.Handley and Dean proposed that the trialkyl thiophosphates probably actby solvating an electrically neutral ion association complex.Ag⁺+NO₃ ⁻ +nTOTP

AgNO₃ nTOTP

The ion association bonding occurs through the P═S group. The semipolarsulphur atom has very little electron donating ability, and will bondonly to ions of high field strength. Silver and mercury fit thiscriteria and also are amongst those metals which prefersulphur-containing ligands. These extractants have been shown to reduceAu (III) to Au°.

Extraction of cadmium, zinc, and mercury have been demonstrated to bepossible with thiophosphorus compounds containing a P—SH group. Theaffinity of these metals for sulphur increases in the orderzinc<cadmium<mercury. The extractants studied included di-n-butylthiophosphite (DBTP) and the di-n-butyl ester of2-hydroxypropan-2-thiophosphonic acid (DBPrPS). It has been reportedthat mercury and gold (III) chloride are extracted from hydrochloricacid solutions with triisobutylphosphine sulphide (Cyanex 471X). Thisextractant is particularly selective for silver and for the separationof palladium and platinum.

In extraction of metal ions from acidic media generally two molecules ofTBP are involved in the extracted species. Furthermore, as the acidconcentration increases so extraction of metal increases until a maximumis reached above which extraction decreases.

In a similar manner, dibutyl butyl phosphonate (DBBP) has been employedfor the extraction of gold, and PGM's, and for zinc. DBBP has a highselectivity and loading capacity for zinc in chloride solutionsresulting from ferric chloride leaching of a complex sulphide ore.Extraction was found to be independent of pH. He reported that two molesof DBBP react with one mole of zinc. As a solvating extractant,extraction occurs as the extractant molecules replace water molecules inthe primary hydration sheath of the extracted species. From thedetermination of free activities of water and free chloride ions it wasshown that four water molecules and two chloride ions are involved foreach extracted zinc species. The extraction reaction may be written asfollows:Zn²⁺+2Cl⁻+2DBBP+4 H₂O

ZnCl₂.2DBBP.4H₂O

DBBP may form dimers at concentrations higher than 3.7×10⁻¹ mol/dm³ andthus at lower concentrations the plot of Log [DBBP] versus Log E astraight line with a slope of two is obtained. At concentrations higherthan 3.7×10⁻¹ mol/dm³ the slope is greater than two possibly because theextraction equilibrium changes in favour of extraction when DBBP dimersform. DBBP may form dimers at higher free DBBP concentrations in amanner similar to that reported by Burger for tributyl phosphate.

Industrial applications of ion exchange resins are many, particularly inthe treatment of boiler feedwater. U.S. Pat. No. 4,069,119 which isincorporated here by reference, describes the application of ionexchange resins to recover copper from dilute solutions emanating fromvat leaching of copper ores. This patent describes the beneficial effectof recovery from solutions containing significant levels of dissolvedsilica. This patent describes ion exchange resins in bead form,including polyurethane foams and porous beads impregnated withconventional organic solvent extraction agents to produce materialswhich may be employed as ion exchange beads in this application.

Other methods for the preparation or application of these polymers aretypically described in U.S. Pat. Nos. 3,793,241; 3,845,535; 3,861,993;3,890,254; 3,900,030; 3,903,232; 3,904,557; 4,110,508; 4,127,516;4,137,200; 4,158,087; 4,160,076; 4,181,770; 4,226,043; 4,292,412;4,314,034; 4,365,025; 4,337,645; 4,384,050; 4,384,051; 4,717,738;4,725,628; 4,731,391; 4,740,528; 4,789,720; 4,798,876; 4,828,542;5,065,752; 5,296,518; 5,591,779; and 5,624,971 incorporated herein byreference.

The procedure for the manufacture of the prepolymers described in theabove patents is either given within the description, or can be producedaccording to typical procedures as described in various publicationsrelating to polyurethane chemistry, or as disclosed in U.S. Pat. Nos.2,726,219; 2,948,691; 2,993,013; 3,805,532 and 4,137,200.

Advantageously the ability to incorporate large volumes of water intoformulation provides an opportunity to incorporate water-based polymeremulsions directly into the polymer. This cannot generally be achievedby the application of conventional polyurethane foams. Water-basedpolymers eliminate the requirement for solvents in the polymerpreparation and therefore eliminate the need to remove and captureenviromentally undesirable solvents. Typically, such emulsions may bewater-based emulsion resulting from the reaction of vinylidenediphosphonic acid with polyurethane foam, offer exceptional selectivityfor Fe(III) in the presence of Cu(II) in acid solutions commonlyencountered in copper electrowinning tankhouse beel streams.

The present invention will now be further described by the followingnon-limiting examples.

EXAMPLES Example 1

A hydrophilic prepolymer “Prepolymer” was prepared by reacting togethera 1000 MW poly(oxyethylene) glycol with toluene diisocyanate to producean isocyanate-terminated prepolymer and then adjusted by the addition ofMDI to produce a finished product with a free NCO content of 9.5%.

PEG1000 100 pbw TDI  44 pbw MDI to provide a Free NCO content of 9.5%

Into a suitable mixing container were added:

Separan Solution (1% in water) 25 g Water 75 g Pluronic L62 1.0 gVitrokele V912 (ion exchange beads) 20 g Ferrosilicon powder 20 gDyestuff 1 drop

The ingredients were thoroughly mixed together and then poured into asecond container containing 50 grams of the following mixture:

Prepolymer 10 g Isonate 143L  1.5 g

The mixture was allowed to rise to form a foam. Pieces were then cutfrom this foam for metal ion loading. Alternatively, the mixture wasallowed to react and cure between two sheets of waxed paper andconstrained in such a manner that a sheet of about 5 mm in thickness wasobtained. This sheet was cut to size.

The polymer produced was used to remove gold cyanide and copper cyanidefrom aqueous solutions and slurries.

Example 2

In the examples in which a liquid organic extract was used, thefollowing procedure was adopted:

XAD-16 (Manufactured by Rohm and Haas) milled 10 g LIX 84I (Manufacturedby Henkel Corporation) 10 g Polyethylene glycol 1000  2 g

The solid resin and the organic extractant were combined together andheated to about 35° C. with constant stirring. Once the extractant wasfully imbibed into the resin, the PBG1000 was added and stirringcontinued. A dry powder was obtained.

This powder was then mixed with the following:

Powder 15 g Ferrochrome 10 g Water 20 g 1% Separan Solution  5 gPluronic L62  0.75 g

To this mixture was added:

Prepolymer 20 g Isonate 143L  5 g

The mixture was allowed to rise to form a foam. Pieces were then cutfrom this foam for metal ion loading. Alternatively, the mixture wasallowed to react and cure between two sheets of waxed paper andconstrained in such a manner that a sheet of about 5 mm in thickness wasobtained. This sheet was cut to size.

The polymer produced was used to remove copper ions from aqueoussolutions.

Example 3

Into a suitable mixing container was added:

Separan solution (1% in water) 6 g Water 60 g Pluronic L62 0.75 g Ionexchange beads with guanidine functionality 20 g Liquid guanidine-basedextractant 5 g Pentanol 5 g PEG1000 5 g Ferrosilicon powder 5 g Dyestuff1 drop

The ingredients were thoroughly mixed together and then poured into asecond container containing 40 grams of the following mixture:

Prepolymer 180 g Isonate 143L  30 g

Example 4

0.1 g of each of the ion exchange polymers described in Examples 1 and3, Vitrokele V912 and guanidine resin (based upon its dry weight) wascontacted with 500 mls of a solution containing 5 ppm gold (as goldcyanide)+200 ppm of CN⁻ (as sodium cyanide), the pH being adjusted to10.6. At the specified time intervals, samples of the aqueous solutionwere withdrawn and analysed by AAS technique. The results obtained aregiven in FIG. 1.

Example 5

The experiments conducted in Example 4 were repeated but in this case,the gold cyanide was replaced with 5 ppm of copper as copper cyanide.The results obtained are give in FIG. 2.

Example 6

A polymer was prepared by:

Styrene-divinyl benzene resin (XAD-7 milled) 10 g LIX 84I 10 g

The solid resin and the organic extractant were combined together andheated to about 35° C. with constant stirring. Once the extractant wasfully imbibed into the resin, a dry powder was obtained.

This powder was then mixed with the following:

Powder 20 g Water 30 g Pluronic L62  0.75 g

To this mixture was added:

Prepolymer 20 g

The mixture was allowed to rise and cure.

Example 7

A reticulated polyurethane foam was imbibed with 25% of LIX 84I and thendipped in a mixture of Prepolymer:water of 1:5, drained and allowed tocure.

Example 8

The LIX 84I syperhydrophilic foams prepared as described in Examples 2,6 and 7 were compared with equivalent weights of commercially availablecopper-selective ion exchange resins as follows:

A feed solution containing 77 ppm copper, 570 ppm iron (as Fe (III)) atpH 2 was contacted with each of the polymers, the experiments beingconducted at room temperature.

After 20 hours the loadings of copper obtained were:

Cu Fe Amberlite IR-120 (sulphonic acid functionality)  4 mg/g 95 mg/gAmberlite IMAC HP 333 (carboxylic acid funct.) 0 mg/g 65 mg/g AmberliteIRC-718 (iminodiacetic acid funct.) 11 mg/g 75 mg/g Example 2 11 m/g 20mg/g Example 6 23 mg/g 25 mg/g Example 7  8 mg/g  0 mg/g

The results given in Examples 1, 3, 4 and 8 indicate that on a ligandfunctional basis, the superhydrophilic foams show faster loadingkinetics and improved loading when compared with the unmodified andcommercially available ion exchange resins.

The results given in Examples 2, 6, 7 and 8 clearly show that theamidoxime-based (LIX 84I) superhydrophilic polymers showed significantlybetter loading of copper and exceptional rejection of iron. Thecarboxylic acid resin initially loaded copper, but this was rapidlyreplaced by iron. The sulphonic acid loaded iron in preference tocopper.

1. A process for the extraction of metal anions and cations fromsolutions and/or slurries including the steps of (a) contacting a metalion-containing solution with an ion exchange material comprising apolyurethane foam having an ion exchange medium contained therein,wherein the foam includes a polyurethane that contains poly(oxyethylene)moieties having a molecular weight of 1,000–1,400; (b) separating theion exchange material from the solution and/or slurry; and (C)recovering the sorbed metal ions from the ion exchange medium.
 2. Aprocess for the extraction of metal anions and cations from aqueoussolutions and/or slurries including the steps of: (a) contacting a metalion-containing aqueous solution with an ion exchange material comprisinga silicone surfactant free polyurethane foam having an ion exchangemedium contained therein, wherein the material has been formed byreacting an isocyanate terminated prepolymer, which is based onpoly(oxyethylene) glycol and isocyanate selected from TDI, MDI,MDI-based isocyanates and mixtures, with an excess of water in thepresence of an ion-exchange medium in the form of a solid ion exchangepolymer, an organic ion exchange liquid absorbed into a solid sorbent ora porous granule, or a water-based ion exchange polymer emulsion, and inthe absence of a silicone surfactant to form the foam; (b) separatingthe ion exchange material from the solution and/or slurry; and (c)recovering the sorbed metal ions from the ion exchange medium.
 3. An ionexchange material comprising a polyurethane foam having an ion exchangemedium contained therein wherein the foam includes a polyurethane thatcontains poly(oxyethylene) moieties having a molecular weight of1,000–1,400.
 4. An ion exchange material according to claim 3 whereinthe ion exchange medium is selected for sorbing metal ions from asolution and/or slurry.
 5. An ion exchange material according to claim 3wherein the ion exchange medium is in the form of a bead, resin, fibre,foam, or liquid.
 6. An ion exchange material according to claim 3wherein the ion exchange medium is in liquid form and is imbibed into asolid sorbent for embedding into the polyurethane foam.
 7. An ionexchange material according to claim 3 wherein the ion exchange mediumis in the form of an emulsion or suspension for imbibing into thepolyurethane.
 8. An ion exchange material according to claim 4 whereinthe ion exchange medium is in the form of a bead, resin, fibre, foam, orliquid.
 9. An ion exchange material according to claim 4 wherein the ionexchange medium is in liquid from and is imbibed into a solid sorbentfor embedding into the polyurethane foam.
 10. An ion exchange materialaccording to claim 5 wherein the ion exchange medium is in liquid fromand is imbibed into a solid sorbent for embedding into the polyurethanefoam.
 11. An ion exchange material according to claim 4 wherein the ionexchange medium is in the form of an emulsion or suspension for imbibinginto the polyurethane.
 12. An ion exchange material according to claim 5wherein the ion exchange medium is in the form of an emulsion orsuspension for imbibing into the polyurethane.
 13. An ion exchangematerial according to claim 6 wherein the ion exchange medium is in theform of an emulsion or suspension for imbibing into the polyurethane.